# 学习网址
# https://liaoxuefeng.com/books/python/introduction/index.html

# def bubble_sort(arr):
#     """
#     冒泡排序算法
    
#     参数:
#         arr: 需要排序的列表
#     返回:
#         排序后的列表
#     """
#     n = len(arr)
#     # 外层循环控制排序轮数
#     for i in range(n):
#         # 设置标志位，用于优化算法
#         swapped = False
        
#         # 内层循环比较相邻元素
#         # 每轮排序后，最大的元素会"冒泡"到最后，所以下一轮可以少比较一次
#         for j in range(0, n - i - 1):
#             # 如果当前元素大于下一个元素，则交换它们
#             if arr[j] > arr[j + 1]:
#                 arr[j], arr[j + 1] = arr[j + 1], arr[j]
#                 swapped = True
        
#         # 如果在一轮中没有发生交换，说明列表已经有序，可以提前结束
#         if not swapped:
#             break
    
#     return arr




# # 测试冒泡排序算法
# print(bubble_sort([64, 34, 25, 12, 22, 11, 90]))
# print(1)
# print(1)
# print(1)
# print(1)
# print(1)
# print(1)
# print(12)
# print(1)
# a='XYZ'
# print(a)


#
# sum = 0
# def calculate_sum(n):
#     sum += (n * n) + 1
#     # 定义一个函数，用于计算x的和
    
#     return sum


# for n in range(1, 101):
#     result = calculate_sum(n)
#     print(result)


# for n in range(1, 51):
#     result = calculate_sum(n)
#     print(result)

# print(sum)

# age = 0xa5b4c3d2
# age = 2880087252
# print(age)

# isOk = 0

# if isOk:
#     print("isOk")
# else:
#     print("isNotOk")

# a =1

# # str a = "abc"

# print(a)

# y = 10
# x = y
# y = 20

# print(x)

# num = "ABC".encode("ascii")
# print(num)


# a = '''hello %s,






#   hi!  THANKS 请支付 %s 元！
  
#   '''

# b = ["jack", "tom", "lucy"]
# for name in b:
#     print(a % (name,1000))


# def test():
#     print('a\r\nb')
        
    

total = 0
for i in range(1, 101):
    if i % 2 == 0:
        total += i
print(total)